Time-restricted eating, also referred to as intermittent fasting, might lead to a decrease in calorie intake, as indicated by the findings of a recent study. Researchers suggest that “counting time is easier than counting calories.”
A study published in JAMA Network Open reveals that individuals with type 2 diabetes (T2D) achieved greater weight loss by consuming unrestricted calories within an eight-hour window compared to those instructed to reduce their calorie intake by 25 percent. Both groups exhibited similar improvements in long-term blood sugar levels, as assessed by hemoglobin A1C, a test reflecting blood sugar levels over the preceding three months.
“Our findings show that time-restricted eating [also called intermittent fasting] is a good alternative to calorie counting for people who can’t do the traditional diet or are burned out on it,” said Krista Varady, PhD. She is the study’s senior author as well as a professor of nutrition at the University of Illinois in Chicago. For many people trying to shed some pounds, counting time more doable than counting calories, she added.
This study demonstrated that time-restricted eating can lead to decent weight loss for those suffering from type 2 diabetes, said Sun Kim, MD, an associate professor of medicine and an endocrinologist who specializes in the treatment of T2D at Stanford University Medical Center in California. “Given that the instructions for time-restricted eating are fairly simple to give and follow, this is a nice option to discuss with patients,” Dr. Kim, who was not part of the research done, said.
New Innovative Strategies to Lose Weight ‘Critically Needed’
Approximately 10% of adults in the United States are estimated to have Type 2 Diabetes (T2D), as reported by the Centers for Disease Control and Prevention (CDC). If present patterns persist, it is projected that by 2050, one in three individuals will be affected by the disease.
Efforts to attain a healthy weight, encompassing dietary modifications, physical activity, weight loss medications, or procedures such as bariatric surgery, can effectively lower blood glucose levels and, in certain instances, result in theremission of T2D. The authors emphasize the pressing need for innovative strategies to assist individuals in achieving and sustaining a healthy weight.
Over 90 Percent of Participants – People of Color
To investigate the effectiveness of time-restricted eating compared to calorie restriction in promoting weight loss and improving blood sugar levels, a study was conducted with 75 participants whose average age was 55 years, average BMI was 39, and HbA1C level was 8.1 percent.
Time-restricted eating involves consuming food and calorie-containing liquids only during specific hours of the day, typically within designated “eating windows” ranging from 4 to 12 hours. In this study, the participants were primarily women (53 subjects), with 40 percent being Hispanic, 53 percent Black, 5 percent white, and 1 participant of Asian descent. The noteworthy overrepresentation of Hispanic and Black individuals is significant as these groups are more prone to diabetes, making studies on the effectiveness of time-restricted eating particularly valuable for them, according to the researchers.
As per the American Diabetes Association, the prevalence of diagnosed diabetes varies among different ethnic groups:
- – Native Americans/Alaskan Natives: 14.5%
- – Blacks: 12.1%
- – Hispanics: 11.8%
- – Asian Americans: 9.5%
- – White individuals: 7.4%
Time-Restricted Eating Group Lost Twice More Weight than Those Who Counted Calories
The study involved the categorization of participants into three distinct groups: those adhering to time-restricted eating, those practicing calorie restriction, and a control group maintaining their regular eating habits.
In the time-restricted eating group, participants were allowed to consume food freely between 12 p.m. and 8 p.m. daily, without the need to track calories or follow specific dietary guidelines. Throughout the 16-hour fasting window, individuals were encouraged to stay hydrated with water and permitted to consume calorie-free beverages. Participants in this group maintained a daily log detailing the timing of their meals.
Meanwhile, those in the calorie restriction group were directed to decrease their calorie intake by 25 percent based on their initial energy requirements, determined at the onset of the trial. For instance, if a person’s baseline energy need was 2,000 calories, their target was to reduce it by 500 calories, aiming to consume only 1,500 calories per day. Members of this group received personalized guidance from a dietitian at the study’s commencement, assisting them in creating individualized weight loss meal plans. Participants logged their daily food intake using a designated app.
Throughout the study, various health indicators such as weight, waist circumference, blood sugar levels, and other relevant metrics were regularly monitored for all participants.
After six months, the time-restricted eating group exhibited a 3.6 percent reduction in body weight, while the calorie-restriction group experienced a 1.8 percent decrease compared to the control group. Notably, both intervention groups showed a 0.9 percent reduction in HbA1C levels, indicating improved blood sugar control.
“We were surprised that the calorie restriction group did not lose more weight. In most studies looking at people with obesity, the time-restricted eating and calorie restriction groups lose the same amount of weight,” Dr. Varady said.
Time-Restricted Eating Easier Than Traditional Diets
Varady suspected that it all boiled down to three reasons. “Looking at the adherence data, the time-restricted eating group was more adherent to their diet than the calorie restriction group,” she said.
Some of the explanation behind this phenomenon might be attributed to the fact that individuals with diabetes are commonly advised by their healthcare providers to initially reduce calorie intake. Consequently, a significant number of these participants may have already attempted—and encountered challenges with—this dietary approach, as suggested by the authors.
“Also, most participants in the time-restricted eating group reported that the diet was easy to follow, and at least half the participants in the calorie-restriction group reported the diet was difficult to follow,” Varady also explained.
Ultimately, the difference may boil down to numerical figures: The calorie-restriction group, on average, lowered their daily intake by just 197 calories, whereas the time-restricted eating group reduced theirs by 313 calories per day.
Weight Loss Was Relatively Modest When Compared With New Weight Loss Drugs
“Intermittent fasting is trendy, and people are eager to try it,” Dr. Kim said. “I think there is better data for earlier time-restricted eating (eating between 8 a.m. to 4 p.m.). However, this time period is harder to adapt, as dinner is a very social meal in our society,” she said.
In Kim’s experience, the rate of success for intermittent fasting (as with many other weight loss interventions) may vary. “Many patients do find it difficult to maintain long term. In the study, people were adherent about six days per week,” she said.
Kim emphasizes that the results underscore the difficulty of losing weight. The weight reduction observed in the time-restricted eating group was relatively modest, at less than 4 percent. This stands in contrast to the effects achieved by currently available GLP-1 receptor agonist medications such as Ozempic, Wegovy, and Mounjaro, which are approved for both diabetes management and weight loss.
Both Groups Shared Similar Average Blood Sugar Reductions
Varady and her team were also surprised to see that though the weight loss had varied, the HbA1C reduction and mean glucose reduction remained similar. “This might be because though the two groups lost different amounts of weight, they had similar reductions in their visceral fat and their waist circumference. We speculate that this might be why their blood sugar improved similarly, even though the weight loss was different on the scale,” she said.
Numerous experts contend that abdominal fat holds significance comparable to Body Mass Index (BMI). Excessive belly fat not only heightens the risk of Type 2 Diabetes (T2D) but is also linked to an elevated likelihood of heart disease and stroke, according to CDC.
Kim pointed out how there may have been several variables that made an impact on blood sugar, including the adjustments for diabetes medications, which seemed to be more for those in the time-restricted group. “Perhaps the greater surprise is that patients in calorie restriction had a meaningful decline in A1C. This may be a tribute to working with dietitians to reduce carbohydrate intake,” she said.
Doing Intermittent Fasting? Speak with a Doctor
No significant adverse events were documented throughout the six-month study. The incidence of both low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia) showed no variation between the diet groups and the control groups.
Varady suggested that, due to the study’s limited size, further investigation through larger studies is warranted. Although this serves as a “proof of concept” indicating the safety of time-restricted eating for individuals with type 2 diabetes (T2D), Varady emphasizes the importance of consulting with healthcare professionals before initiating such a diet.
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